Comparative Accuracy of the Barrett Toric Calculator With or Without the Incorporation of Posterior Corneal Astigmatism and the Castrop Formula.

PURPOSE: To compare the predictive accuracy of the Barrett Toric IOL formula-when incorporating either Predicted or Measured posterior corneal astigmatism (PCA)-with the Castrop Toric formula.

METHODS

In this retrospective study, patients diagnosed as having age-related cataract who underwent phacoemulsification with the implantation of a monofocal non-toric IOL were reviewed. Four methods of calculating a toric IOL-the Castrop formula based on Predicted PCA (C-PPCA), the Castrop formula based on Measured PCA (C-MPCA), the Barrett Toric Calculator based on Predicted PCA (B-PPCA), and the Barrett Toric Calculator based on Measured PCA (B-MPCA)-were applied to calculate the predicted residual astigmatism and spherical equivalent (SE). The mean absolute astigmatic prediction error (MAPEastig), centroid of astigmatic prediction error (PE), proportion of eyes within the astigmatic prediction error of ±0.50, ±0.75, and ±1.00 diopters (D), and PE of SE were all calculated for the four methods.

RESULTS

One hundred eyes of 100 patients were reviewed. No significant differences were seen for MAPEastig (P = .379) or the centroid vectors of astigmatic PE among the four methods (P = .138), although the differences of the predictability rate within ±1.00 D were significant (P = .008). B-PPCA and B-MPCA yielded better clinical results, with 89% and 90% of eyes achieving an astigmatic PE of less than 1.00 D, compared to that of the Castrop Calculator (P = .006 and P = .002, respectively). For the 71 eyes with axial length of 22 to 26 mm and anterior corneal refractive power of 42.00 to 46.00 diopters, no significant differences in the PE of SE were seen between B-PPCA and B-MPCA (P = 1.000), or between C-PPCA and C-MPCA (P = .078). Further comparison showed that the PE of the SE of the Castrop Calculator was significantly greater than the Barrett Toric Calculator (P < .001).

CONCLUSIONS

The current study revealed comparable outcomes of the accuracy of cylindrical power calculation between the Barrett Toric and Castrop Calculators, both using Predicted and Measured PCA mode, although the Barrett Toric Calculator showed a lower PE than the Castrop Calculator in IOL spherical power calculation.